Conventionally, a terminal block of a type in which screws are inserted into holes of ring terminals and the screws are fixed to threaded holes of contact seats is widely used. In these terminal blocks, to install the screws when they are completely detached from the contact seat, the screws need to be inserted into the holes of the ring terminals, and then screwed into the contact seats in order to fix the ring terminal. This multistep process results in a process-heavy workload required to mount the ring terminal.
Alternative designs of a terminal block of a type that can reliably fix ring terminals with fewer steps is desired. While several alternative designs have been developed to solve this long-felt need in the industry, none of these designs offers the reliability desired, while reducing the number of assembly steps.
For example, Japanese Patent Application No. 2000-306617 (“Reference 1”) discloses a relay ground terminal for a residential distribution board. A ground wire is inserted into a housing, and a locking metal element is crimped to the ground wire by rotationally operating an operation lever. The operation lever is equipped with a cam face to drive an auxiliary member to the ground wire. While this design reduces the number of assembly steps, reliability is not increased, because the ring terminal can be pulled out when the ground wire is pulled with a sufficient force.
Japanese Patent Application No. 2007-165323 (“Reference 2”) discloses an electrical terminal in that uses an operation cam to fasten a conductor, where the conductor is fastened through a pivoting action of the operation cam. The conductor is inserted into a through-hole, and the operation cam is rotationally operated to produce a camming action that fastens the conductor.
Further, Japanese Patent Application No. 2008-64266 (“Reference 3”) discloses a terminal device in which a conductor is secured by insertion into a locking hole of a locking spring. A release lever having a cam is rotationally operated to fasten the conductor through the pivoting action of the cam spaceion.
Similarly to Reference 1, References 2 and 3 also suffer from the ring terminal being pulled out accidentally when the conductor is pulled on. Further, since the insertion direction of the electric wire is different from the direction of a rotation axis of the cam, it is difficult to achieve a low profile terminal block.
Therefore, a terminal block is needed to reliably hold a conductor and to do so using a minimum number of steps.